Hundreds of years ago, mankind embarked on the road of technological development, and the advent of the industrial age also gave people the hope of exploring the universe. With the help of science and technology, in the middle of the last century, mankind finally walked out of the earth and began to explore the universe.
The universe is vast and mysterious. Although we can observe the depths of the distant starry sky through astronomical telescopes, we still need to get out of the earth and get close to the universe if we want to truly understand the universe. Therefore, sending astronauts into space is an important step in our exploration of the universe.
To send astronauts to space and return to the ground completely after completing the mission, a spacecraft is needed. This kind of spacecraft is different from the aircraft we know. The aircraft can take off and land directly from the ground, but the spacecraft cannot. It needs the boost of a rocket.
Entering space from the ground with the assistance of a rocket can enter the predetermined orbit more accurately, but when the astronauts need to return to the earth for a complete mission, the landing point of the spacecraft is not accurate, and sometimes the deviation will be very large. I believe my friends all know that whether it is the return of the American Apollo spacecraft or the return of my country’s Shenzhou spacecraft, a large number of people and equipment will be dispatched, and the United States will dispatch aircraft carrier formations.
So a friend raised the question: Why is the landing point of the spacecraft inaccurate when it returns to the ground? If the landing point can be accurately located at one location, it will not be necessary to mobilize a large number of people and various motor vehicles with great fanfare. Some friends even said that a positioning system can be installed on the spacecraft, so that the position can be accurately known when landing on the ground.
Landing the spacecraft in an accurate position is naturally a very good thing, but why can’t it be done in reality? In fact, this is caused by multiple reasons. After mankind entered the age of science and technology, the relatively high-tech means of transportation should be airplanes, which are the crystallization of human wisdom.
Only with airplanes, we have the hope of traveling all over the earth, and we can turn the earth into a global village. The distance between people and the distance between regions are also shrinking. Now as long as you want, you can quickly reach any corner of the earth’s surface in an airplane, and we also know that when the airplane needs to land, it can accurately reach the destination, and there will be little deviation, unless it is an emergency or an accident. It will fall outside the airport under the circumstances.
The plane can land accurately on the runway of the airport from high altitude, but why can’t the spacecraft? To understand this problem, we must have an understanding of the aircraft’s landing mode. The aircraft can accurately land in the airport because its orbit can be actively adjusted during the landing process.
We all know that airplanes can glide at low speeds in the atmosphere, and there is a lot of choice in the process of gliding. Even if there is a deviation, the descending trajectory can still be corrected and finally landed accurately to the target position. But the spacecraft can’t do this, it’s mainly related to the shape of the spacecraft.
I believe many friends know that the shapes of the spacecraft are similar. The Apollo series have a conical outsole, while the Shenzhou series in my country are bell-shaped. No matter what kind of spacecraft they are, they cannot glide at low speeds in the atmosphere. To adjust the orbit of the spacecraft, it can only be done before it enters the atmosphere. For example, my country’s Chang’e-5 returned to the low-Earth orbit and made two rebound adjustments.
After the spacecraft completes its orbit adjustment in space, it begins to quickly enter the atmosphere. At this time, the spacecraft is like a weighing mound. It can only fall down in a free fall, and cannot control its footing at all, nor can it orbit in the middle. Adjustment. When it reached a height of 10,000 meters, the parachute opened and slowed down continuously, and finally landed on the ground.
The landing method of a spacecraft after entering the atmosphere is equivalent to a parachuting mode, and the location of the landing point of the parachuting is completely impossible to accurately locate, and it will be affected by many aspects. If the weather at that time has relatively strong winds, the landing point may drift far away.
Of course, by adding various factors to the landing point of the spacecraft, and then through scientific calculations, it is still possible to roughly calculate the position. After determining the general location, dispatched motor vehicles and personnel to wait in the target area. A friend said: Why not install a positioning system for the spacecraft? So we can know its location accurately.
In fact, this is a misunderstanding of people. The weight of the wireless positioning system is not large, and it is not a matter to install one on the spacecraft. But is this necessary? In fact, it is not necessary. The current satellite positioning system is very advanced, and it can basically track the spacecraft’s return process throughout. Moreover, the return of the spacecraft from space to Earth is not a random thing, but can only be carried out after a lot of calculations.
The spacecraft can only change its orbit in space, so before entering the atmosphere, the spacecraft on the ground has set a range in advance for the spacecraft’s landing point. Then, according to this setting, let the spacecraft complete its orbit change in space, so that the return position of the spacecraft after entering the atmosphere is generally determined. Generally, it is selected to be in grass or desert areas, avoiding densely populated areas, otherwise it will hit people and objects. That’s not good.
Since the return of the spacecraft cannot make an accurate landing, why don’t we use the space shuttle to return to Earth? The space shuttle believes that some friends also know that it is a spacecraft similar in appearance to an airplane, capable of glide at low speeds, and can also perform orbit corrections in the middle. Therefore, the space shuttle can land to a predetermined position relatively accurately.
Such a good space shuttle, why don’t astronauts use it when entering and exiting the earth? There are two main reasons for this. One reason is that the space shuttle is a gold swallowing beast, and it requires a lot of money whether it is research and development, use or later maintenance. The cost of each launch is about 500 million U.S. dollars, and the maintenance cost after use is also very high, and the life span is still lower than expected.
Another reason is that the space shuttle is not as safe as the spacecraft. The explosion of the American Challenger and Columbia space shuttles made people see their insecurity, and the space shuttle was eventually retired. Regardless of money or safety, spacecraft is the first choice for mankind’s current technology.
Of course, it is inevitable that the space shuttle will replace the spacecraft in the future. After all, human beings speed up the pace of exploring the universe, and it is obviously impossible to use a spacecraft every time it enters and exits the earth. However, the use of space shuttles requires the emergence of more powerful energy sources. The chemical energy we use now requires rockets to send astronauts into space.
It is because the energy level of chemical energy is not enough that the cost of using the space shuttle is very high, and it is not safe yet. Only a stronger energy-loaded power system can easily send the space shuttle into space and return to Earth easily. Only by realizing the free access of the space shuttle can human beings truly start the era of space exploration.
And this powerful energy is the controllable nuclear fusion that scientists have been researching and exploring. The powerful energy of nuclear fusion can completely get rid of our dependence on rockets, allowing the aircraft to enter and exit the earth freely without the aid of rockets. Therefore, when the space shuttle can completely replace the spacecraft, it mainly depends on when the controllable nuclear fusion can be realized.